As an apparatus to prevent phone call frauds, Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-196949) discusses a telephone set that is configured to give a warning based on contents of a phone call. The telephone set includes a word register for keywords to be detected from calling voice data, so that, if a keyword in the word register is found in calling voice data, the set gives a warning.
Patent Document 2 (Japanese Patent Application Laid-Open No. 2008-210085) discloses an apparatus configured to determine whether or not contents of a phone call relates to fraud based on detection of a keyword from calling voice data and references to voice print database and bank account database.
In the configuration discussed in Patent Document 1, abnormality such as fraud is detected only based on keyword detection that is obtained through voice recognition of calling voice data. Accordingly, in the cases with unclear voices or low S/N ratios of calling voice data, the accuracy of voice recognition and thus the accuracy of abnormality detection are reduced.
In the configuration discussed in Patent Document 2, recognition of information other than keywords is used for improved accuracy of abnormality detection. The approach, however, requires collections of information for constructions of keyword dictionary, voice print database, bank account information database, and the like, which requires constant update of the databases for current information. As a result, the apparatus using the information such as keyword, voice print, bank account number cannot be completely caught up with before it is used in new fraud.